So I have an A4 (2013 B8.5) with an RSNav MMI system installed. I've recently decided to install a reverse camera (or "backup camera) so ordered one off eBay.

The one I odered was something like this that has a long composite wire (with a short red power wire on each end) and a power connector on the camera end. Pretty standard layout. The wire harness for the RSNav conveniently includes wires for a front/rear camera. And I'm finding it confusing as to how to wire this thing in.

It recommends that you wire it to your reverse light for power. I'm a bit sceptical about this, but I did try it. However when engaging reverse nothing at all happened on the RSNav. Not sure if I wired it incorrectly or need to set something up; looked through the system to find some kind of configuration but not really much relating to engaging camera when reversing. I figured it would detect the video feed when engaging reverse.

I'd much prefer to use the wiring from the RSNav but it only has +12v for the rear camera, what about the ground?

I've attached a pic of the RSNav wire description, but note that there's no ground wire, even though it's included. I havent got the best understanding about how this all works and it's driving me mad because there's a complete lack of information relating to wiring an aftermarket camera into an RSNav. The few results I've found mention anything from installing diodes, relays and all kinds. It's all a bit confusing and would appreciate someone to shed some light on the situation.


RSNav wires

 

So for anyone interested I've sorted it now.

Going into this with not much knowledge about it wasn't the best idea. The diode is apparently on the camera detection wire to stop the Audi system detecting any abnormality. I tried hooking it up via the reverse light as described. This did kind of work, but the screen wasn't very clear and when you started the engine it just went haywire... The screen become indistinguishable and you could even hear a buzzing.

So it seemed that you could use a 12v filter (capacitor) to smooth the voltage out which fixed the issue for most people. After getting one off eBay and install it it seemed to work. However, now the picture would turn off after a few seconds, come back on, then turn off again... and so on. Measuring the voltage coming out the filter was only around 8v (for some reason). It seemed to me that the voltage still didn't seem to be stable, either. So I ordered another filter (12~15v this time) fit that one (once it came) & this time made sure it was 12v output. Yes great; tried it again and you wouldn't believe it was still doing the exact same thing. I relocated the camera detection wire from the reverse light to the +12v output of the filter with the same damn results.

So I decided to isolate the wiring; getting +12v directly from the battery and also using the batteries negative instead of using the car body as ground. Conveniently the battery is located directly in the boot so it wasn't too much of a hassle. Extending the wiring and chucking on some proper terminals I connected the camera to the battery (still using the 12v filter) but now via a relay. So the only thing coming from the reverse light was the relay trigger.

And success! After being so close to giving up it finally works. Nice constant clear picture.

I've included a hilariously crude diagram of the wiring, as funny as it is it could help someone attempting the same thing:

 

I've also installed an aftermarket camera and done so at the same time as installing a Wireless Carplay box. The Camera is powering Ok, but I cant figure out how to get the detection bit working. Can you explain the bit about the detection wire? I have an A4 B8 with MMI 3G if that has any bearing on it

John